1. Field of the Invention
The present invention relates to a system and method for calibrating charge-regulating module, and more particularly to a charged particle beam system with a calibratable charge-regulating module.
2. Description of the Prior Art
Improvements in the semiconductor manufacturing technology have allowed for designing and manufacturing of higher density integrated circuits and packing more transistors on a given surface area to form a semiconductor device or chip. Increasing transistor density on a given chip has led to the need for method to provide electrically related, higher resolution wafer inspection. In semiconductor device manufacturing processes, defects may be unintentionally generated during the various stages of semiconductor processing. Thus, it is important to find defects accurately and efficiently as early as possible. Generally, a process for manufacturing semiconductor devices comprises the operation of forming layers of a variety of materials on or in the substrate of each semiconductor device; photo-processing, masking and forming circuit patterns on the semiconductor device; and removing or etching portions of the layers to form the semiconductor device. Such semiconductor devices are manufactured by repeating these and other operations on each device of a semiconductor wafer. Better manufacturing techniques have allowed for micro fabrication, resulting in features that are much less visible by most observation tools. Inspections of the wafer are made to check for obtaining defect free devices. In view of this requirement, charged particle beam systems, e.g. scanning electron microscopes (SEMs), electron beam probers and focused ion beam (FIB) systems, are used in such purpose.
Charges on a wafer sample may be accumulated when scanned by the current charged particle beam tools, particularly for the ebeam inspection tool due to larger beam current requirement, and quality of the acquired image will thus be deteriorated due to the accumulated charges on the surface of the wafer sample. Critical defects then can be hardly identified. In order to get rid of this issue, a charge regulation method is provided to regulate or control charge conditions wafer surface. One charge regulation module is to use Laser illuminating onto the wafer surface, and charged can be regulated due to photoconductivity and/or photoelectric effect.
However, after the charge regulation module is mounted to the charged particle beam tool, the illuminated area by Laser may be deviated from the point irradiated by the charged particle beam on the wafer surface due to installation or operation of the charged particle tool, and charge conditions thereon may be again deteriorated little by little. A calibration is thus necessary. Nevertheless, the charged particle tool is built within a vacuum chamber, and the calibration procedure of charge-regulation module means to breakdown the vacuum environment to atmosphere in the chamber. After the charge-regulation module is calibrated, the chamber has to be processed to vacuum environment. Such a calibration procedure is a time-consuming schedule, about 2-days or longer.
Therefore, it is desirable to provide a method a system for calibrating the charge regulation module in the charged particle beam tool.